Wiring Connections for an Electric Water Heater

What are the Wiring Connections for a Water Heater? The Electrical Connections for a 50Gal 240 Volt Electric Water Heater.

Electric Water HeaterElectrical Question: How should I wire a 50Gal Water Heater?

I’m connecting an electric water heater to the electrical junction box. I have a A. O. Smith 50 Gal Water Heater that has a red and black wire. The electrical junction box has red, black, white and ground. Please give advise.

How to Wire a Water Heater

Skill Level: Intermediate to Advanced – Best performed by a Licensed Electrician.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on the personal level experience and ability to work with tools and access to the wiring.
Precaution: Identify the water heater circuit, turn it OFF and then Tag it with a Note before performing any wiring.
Special Materials: Properly sized wire connectors and a blank cover.

Electrical Connections for a 50Gal Water Heater

Identify the circuit for the hot water heater and make sure it is turned off.

If the incoming electrical circuit has a black, red, white and ground wire then the white or neutral wire is caped off and not connected unless your water heater requires a separate neutral wire.

The bare ground wire of the incoming circuit is bent into a clockwise hook shape and placed under the green ground screw and secured tightly. This screw is located inside the water heater junction box, or the water heater may have a green ground wire that may be used.

The typical 240 volt water heater has a red and black wire located in a junction box at the top of the water heater.

The incoming circuit wires and the water heater wires are normally black and red, and are splices or connected together, color to color using red or gray wire nuts.

If the incoming electrical circuit wiring does not have a separate red wire, then the white wire may be used as the second 120 volt circuit of the 2-pole 240 volt circuit, and should be indicated with a black or red wrap of electrical tape of permanent marker. If unsure about the incoming circuit then the circuit should be verified by an electrician with a voltage tester.

Hooking Up a Water Heater
I hooked up a water heater to an existing 3 prong outlet. The water heater only requires 2 hot 120 volt wires to heat water and function. The only other wire to connect is the wire that goes to the metal case of the water heater where there’s a green screw. I believe the center wire on the 3 prong outlet is a neutral wire and I’ve read that using neutral for chassis ground is never a good idea. The outlet also has a bare copper wire so this is where the ground wire should connect. Or I’ve been told to connect the green screw to the incoming cold water pipe. If a hot wire or some kind of malfunction, water leak causes voltage to make contact with the metal case, without the ground wire the metal is now hot and would cause anyone who touches the case to get shocked. So I’m thinking more than one ground on a water heater would be bad because now the ground at the panel is sharing a ground with the water heater so there should only be one ground. The question is what is more reliable to use. The cold water pipe or the bare ground wire through the outlet.

Water Heater Circuit
Hi JG,
A typical water heater requires a 30amp 240volt dedicated circuit which includes a ground wire. The proper installation of a dedicated water heater circuit will not require an additional ground source if the electrical panel the circuit is connected to has an approved bonded ground system as required by the NEC code.
I hope this helps you,
Dave

Water Heater Electrical Junction Box
Hi Tom,
Most conventional electric water heaters have a built in junction box located in the top of the unit. At the point of connection, there is typically a knock-out opening where a flex conduit with the circuit wiring may be attached directly to the water heater. Therefore, a junction box is not necessary. However a junction box may be installed where the circuit wiring is located at the water heater which will enable you to transition to the flex conduit which will then attach to the water heater.
I hope this helps,
Dave

Water Heater Electric Circuit has a White Wire
I have 3 wires coming out of my wall: a bare copper wire, a white wire, and a black wire. my water heater has 3 wires colors which are a red wire, a green wire, and a black wire, what connects with what?

Verify the Water Heater Electric Circuit
Hi Miguel,
The wiring at the wall should be verified to make sure that they belong to a dedicated circuit which is designated for a water heater.
Even though there is a typical 30 amp 240 volt water heater circuit that is installed in many homes, it should be noted that all electric water heaters are not the same and some will have specific circuit requirements, therefore you should verify the circuit requirements of your water heater and then compare the specifications to the circuit wiring which you have described to make sure the circuit is fully compatible.
Note: Many of the older 30 amp 240 volt dedicated water heater circuits consisted of a 2-wire with ground cable, which consisted of a ground wire, a black wire, and a white wire, and in these circuits the white wire was normally connected to the red wire of a 240 volt water heater, however as described in the preceding, the circuit must be positively verified first. In newer installations where there is a 2-wire with ground cable for a 240 volt water heater the white wire is colored with red electrical tape which clearly designates it’s part of the 240 volt circuit. Identifying the circuit wiring with red electrical tape is important and should be applied to existing circuit wiring as needed.
I hope this helps,
Dave

Water Heater Thermostat Controls
I have an old Basmore Electric Water Heater. There are four wires that run into the control section of the water heater from the junction box on the heater. Two of these go to the top terminals on high temp cutout of the thermostat. The third goes directly to one side of the upper element. The fourth goes directly to one side of the lower element. The upper thermostat is faulty, but I can find a replacement that is exactly the same. And all the wiring diagrams I can find do not have these third and fourth wires going directly to the elements. Anyone have any advice?

Water Heater and the Neutral Wire
The comment asking why a neutral is not used for the 240 volt circuit of an electric water heater refers to the neutral wire being used as the return path of the electrical current. This may be true in the case of a 120 volt circuit, however a 240 volt water heater does not need a neutral wire because the heating elements are 240 volts. Unlike a new electric dryer for example, which has a 120 volt control timer, an electric water heater does not yet have 120 volt controls. The 240 volt heating elements of the water heater are similar to most kitchen ranges and cook tops which have 240 volt heating elements which do not require a neutral wire as well. The thermostat controls for most of these types of devices control the temperature by making or breaking one leg of the 240 volt circuit. A simple explanation of power generation of Alternating Current, or AC Power, is that each leg of electrical power that is being produced is out of phase compared to each other leg of the power being generated.
I hope this helps,
Dave

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